The density of airport traffic is ever greater both in the air and on the ground. Collisions between aircraft and various obstacles on the ground are ever more frequent, notably when an aircraft attains a parking position from an airport landing runway. For example, on a wide-bodied aircraft, it is hard for the pilot of the aircraft to see the wings and engines. The wings and engines are therefore particularly exposed to impacts with various objects such as:                other aircraft;        airport installations;        technical vehicles of the airport.        
This type of incident, in addition to the costs of repairing the aircraft, gives rise to the grounding of the aircraft. This grounding of the aircraft is financially prejudicial to the company owning this aircraft.
To alleviate these collision problems, airports are furnished with various means allowing centralized management of the traffic on the ground. These means are notably airport monitoring radars, radio means, GPSs and transponders. However, the density of the traffic on the airports is such that these means are insufficient to ensure the final guidance of aircraft towards their parking position. Moreover these means are often ineffective in foggy weather for example and generally when the meteorological conditions are bad or at nightfall. Human intervention is then necessary in order to avoid any risk of the aircraft colliding with objects present on the ground in a taxi zone.
Another way to avoid collisions between an aircraft and objects present on the ground is to equip the aircraft with autonomous anticollision devices complementary to the means existing at the airport. These anticollision devices make it possible notably to ensure the protection of the aircraft over a very short distance in relation to objects that are fixed or possess a low speed of movement.
Among these means, devices comprising cameras are notably used. Cameras are, however, ineffective with poor meteorological conditions. Moreover, devices based on cameras do not provide the pilot with accurate information either on the distance between the aircraft and a potential obstacle, or on the relative speed of the aircraft with respect to the obstacle. To process a wide angular domain with a sufficient depth of field in a very short time, cameras can be equipped with zooms or fast electronic pointing devices. Cameras thus equipped are complex to implement and do not possess the reliability necessary for an anticollision device.
Other devices based on LIDAR, standing for Light Detection And Ranging, can be used. Anticollision devices using LIDAR have, however, the same drawbacks as devices using cameras.
Acoustic sensors can also be implemented in anticollision devices. Acoustic sensors are, however, very sensitive to jamming and to disturbances in the propagation of acoustic waves. All this makes it difficult to employ acoustic sensors in an airport environment. The range of the acoustic sensors is also too low, of the order of a few meters, to be suitable for an anticollision device.
Other anticollision devices use radar technologies such as ultra wideband radars. These devices risk jamming other equipment such as the navigation equipment on board the aircraft. Ultra wideband radars are therefore subject, when their use is permitted, to very restrictive regulation limiting notably the power of the emitted wave. The limitation of the emission power of these radars considerably reduces their domain of use and notably their range. Moreover, these radars do not possess, taken individually, any angular discrimination capability. They therefore do not allow sufficiently accurate location of obstacles. Such radars possess beneficial angular discrimination capabilities only when they are grouped into arrays of large dimension, this being impossible to implement onboard an aircraft.